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DOE OSTI2017

Preparation and characterization of RF magnetron sputtered CuO/CaTi{sub 4}O{sub 9} thin films with enhanced third-order nonlinear optical properties

The titanate, is a material of interest for various energy applications, including photovoltaics, catalysts, and high-rate energy storage devices. Herein, its related materials, CuO/CaTi{sub 4}O{sub 9} [CCTO] thin films, were successfully fabricated on SrTiO{sub 3} (100) substrates by RF magnetron sputtering assisted with subsequent oxygen annealing. This obtained CCTO thin films were then systemically studied by X-ray powder diffraction (XRD), atomic force microscopy (AFM), scan electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). It was found that CuO and CaTi{sub 4}O{sub 9} (001) particles were closely accumulated together on the surface of the substrate in the annealing process after comparing with that of the as-prepared thin film, which was verified by SEM and AFM results. Furthermore, we investigated the third-order nonlinear optical (NLO) properties of the as-prepared and annealed CCTO thin film by means of the Z-scan technique using 650 nm femtosecond laser pulse. Post-deposition oxygen annealing was found to modify the morphological characteristics of the films, resulting in enhancing their NLO properties. The observation of NLO performance of annealed CCTO thin film indicates that RF magnetron sputtering is a feasible method for the fabrication of optical thin films, which can be expanded to fabricate other NLO materials from the corresponding dispersions. Naturally, we concluded that the CCTO thin film occupy a better NLO property, and thus enlarge its application in nonlinear optics. - Highlights: • The CCTO thin film was prepared using the RF magnetron sputtering and oxygen annealing. • The film was prepared on the SrTiO{sub 3}(100) substrates with a Ca{sub 2}CuO{sub 3} target. • The oxygen annealing was found can effectively enhance the film quality and NLO property. • The film was characterized using XPS, SEM, AFM, TEM, XRD and Z-scan techniques.

36 MATERIALS SCIENCE↗

DOE OSTI2024

Magnetron sputter deposition of boron carbide in Ne and Ar plasmas

Conventional magnetron sputter deposition of B 4 C uses Ar as the working gas. In this report we explore the magnetron sputter deposition of B 4 C with a Ne plasma, which is expected to exhibit larger sputtering yields than Ar. We study properties of films deposited with different substrate tilt angles with the magnetron source operated in either direct-current (DC) or radio-frequency (RF) mode in an Ar or Ne plasma. Results show that the B 4 C film properties are determined by a combination of sputtering ballistics and effects of the working gas on the plasma discharge and gas phase scattering of depositing species flux. At constant discharge power, deposition rates for Ar and Ne plasmas are similar, which is attributed to balancing effects of a higher ballistic sputtering yield of Ne and lower ion flux to the target. Both depositing B and C neutral species and bombarding ions have higher energies for the case of Ne plasmas. Films deposited with the RF-driven Ne plasma exhibit a uniform non-columnar structure, lowest oxygen impurity content, and highest mass density and mechanical properties at a cost of Ne incorporation and larger compressive residual stress.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Synthesis of Highly Oriented Zinc-Oxide Films on Amorphous Substrates by the Method of Direct-Current Magnetron Sputtering

We describe the technology of obtaining highly oriented zinc-oxide (ZnO) films on amorphous substrates at high growth rates (up to 7 nm/s) by means of direct-current magnetron sputtering. It is suggested to optimize the substrate position with respect to magnetron and consider the floating potential to which the substrate is charged in magnetron discharge plasma as one of the main technological parameters. Electrondiffraction study of the structural characteristics of the obtained ZnO films showed that increase in the substrate temperature was accompanied by transformation of the crystallite shape from platelike to columnar.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2025

Effects of substrate bias and tilt on magnetron sputtered boron carbide films

Maintaining high density and good mechanical properties at oblique angles for magnetron sputtered amorphous boron carbide films remains a challenge. In this study, we investigate the effect of the substrate bias on density, residual stress, mechanical properties, and morphology of boron carbide films deposited via direct current magnetron sputtering with a full-face erosion magnetron source in a mixed Ar-Ne plasma. Results show that films deposited at oblique substrate tilt angles on substrates biased at -50 V possess significantly lower oxygen content, superior mechanical properties, and higher density compared to their electrically grounded counterparts. In conclusion, these enhancements observed at oblique angles, while promising, come at the cost of larger residual compressive stress and higher Ne incorporation in films.

Materials science↗

DOE OSTI2018

INJECTION LOCKED 1497 MHZ MAGNETRON

A novel injection-locked 1497 MHz 13 kW AM magnetron design is presented. An anode designed to minimize eddy currents due to the modulated magnetic field is presented. Thermal calculations of two design options are also presented. An extra degree of freedom in the anode construction is made possible by the fact that the magnetron is injection locked; as a result some additional design details that can be utilized in the cooling network for the magnetron anode are presented.

Wang, Haipeng↗

DOE OSTI2024

PROGRESS ON MAGNETRON R&DS FOR INDUSTRIAL PARTICLE ACCELERATORS

The magnetron as an efficient RF source for a compact industrial SRF accelerator has been developed. The per-formance of injection phase lock on two independent magnetron transmitters operated at 915MHz, in CW mode with maximum power of 75kW each has been demon-strated to satisfy this application. This industrial type magnetron has AC transformer and the SCR rectifier on the DC anode power supply. Output power spectrum with phase locking can achieve noise reduction of -21.2 dBc at the 1st 60 Hz, -28.0 dBc at 1st 180 Hz with only -22.6 dBc injection power. Further control studies for 2×75 kW, 915 MHz power combing by WR975 magic-tee at Jefferson Lab (JLab) and for 4×1.2 kW, 2.45 GHz power combing by WR340 magic-tee at General Atomics (GA).

Rimmer, R.↗

DOE OSTI2020

A 100 kW 1.3 GHz Magnetron System with Amplitude and Phase Control

Calabazas Creek Research, Inc., Fermilab, and Communications & Power Industries, LLC, developed a 100 kW peak, 10 kW average, 1.3 GHz, magnetron-based, RF system for driving accelerators. Efficiency varied between 81% and 87%. Phase locking uses a novel approach that provides fast amplitude and phase control when coupled into a superconducting accelerator cavity [1]. The system was successfully tested at Fermilab and produced 100 kW in 1.5 ms pulses at a repetition rate of 2 pps. A locking bandwidth of 0.9 MHz was achieved with a drive signal of 269 W injected through a 4 port circulator. The phase locking signal was 25 dB below the magnetron output power. The spectrum of the phase locked magnetron was suitable for driving accelerator cavities. Phase modulation was demonstrated to 50 kHz (the limit of the available driver source). The average power was limited by available conditioning time. Scaling indicates 42 kW of average power should be achievable. Estimated cost is less than $1/Watt of delivered RF power, exclusive of power supplies or modulators. System design and performance measurements will be presented.

43 PARTICLE ACCELERATORS↗

DOE OSTI2022

Magnetron R&D Progress for High Efficiency CW RF Sources of Industrial Accelerators

After the demonstration of using high efficiency magnetron power to combine and aim to drive a radio frequency accelerator at 2450MHz in CW mode [1], we have used trim coils adding to a water-cooled magnetron and three amplitude modulation methods in an open-loop control to further suppress the 120Hz side-band noise to -46.7dBc level. We have also successfully demonstrated the phase-locking to an industrial grade cooking magnetron transmitter at 915MHz with a 75kW CW power delivered to a water load by using a -26.6dBc injection signal. The sideband noise at 360Hz from the 3-Phase SCRs DC power supply can be reduced to -16.2dBc level. Their power combing scheme and higher power application to industrial accelerators are foreseeing.

Wang, H.↗

DOE OSTI2017

Implementation of Design Changes Towards a More Reliable, Hands-off Magnetron Ion Source [Slides]

As the main H- ion source for the accelerator complex, magnetron ion sources have been used at Fermilab since the 1970’s. At the offline test stand, new R&D is carried out to develop and upgrade the present magnetron-type sources of H- ions of up to 80 mA and 35 keV beam energy in the context of the Proton Improvement Plan. The aim of this plan is to provide high-power proton beams for the experiments at FNAL. In order to reduce the amount of tuning and monitoring of these ion sources, a new electronic system consisting of a current-regulated arc discharge modulator allow the ion source to run at a constant arc current for improved beam output and operation. A solenoid-type gas valve feeds H2 gas into the source precisely and independently of ambient temperature. This summary will cover several studies and design changes that have been tested and will eventually be implemented on the operational magnetron sources at Fermilab. Innovative results for this type of io n source include cathode geometries, solenoid gas valves, current controlled arc pulser, cesium boiler redesign, gas mixtures of hydrogen and nitrogen, and duty factor reduction, with the aim to improve source lifetime, stability, and reducing the amount of tuning needed. In this summary, I will highlight the advances made in ion sources at Fermilab and will outline the directions of the continuing R&D effort.

43 PARTICLE ACCELERATORS↗

DOE OSTI2017

Implementation of Design Changes Towards a More Reliable, Hands-off Magnetron Ion Source

As the main H- ion source for the accelerator complex, magnetron ion sources have been used at Fermilab since the 1970’s. At the offline test stand, new R&D is carried out to develop and upgrade the present magnetron-type sources of H- ions of up to 80 mA and 35 keV beam energy in the context of the Proton Improvement Plan. The aim of this plan is to provide high-power proton beams for the experiments at FNAL. In order to reduce the amount of tuning and monitoring of these ion sources, a new electronic system consisting of a current-regulated arc discharge modulator allow the ion source to run at a constant arc current for improved beam output and operation. A solenoid-type gas valve feeds H2 gas into the source precisely and independently of ambient temperature. This summary will cover several studies and design changes that have been tested and will eventually be implemented on the operational magnetron sources at Fermilab. Innovative results for this type of ion source include cathode geometries, solenoid gas valves, current controlled arc pulser, cesium boiler redesign, gas mixtures of hydrogen and nitrogen, and duty factor reduction, with the aim to improve source lifetime, stability, and reducing the amount of tuning needed. In this summary, I will highlight the advances made in ion sources at Fermilab and will outline the directions of the continuing R&D effort.

43 PARTICLE ACCELERATORS↗

DOE OSTI2018

Improved Magnetron Stability and Reduced Noise in Efficient Transmitters for Superconducting Accelerators

State of the art high-current superconducting accelerators require efficient RF sources with a fast dynamic phase and power control. This allows for compensation of the phase and amplitude deviations of the accelerating voltage in the Superconducting RF (SRF) cavities caused by microphonics, etc. Efficient magnetron transmitters with fast phase and power control are attractive RF sources for this application. They are more cost effective than traditional RF sources such as klystrons, IOTs and solid-state amplifiers used with large scale accelerator projects. However, unlike traditional RF sources, controlled magnetrons operate as forced oscillators. Study of the impact of the controlling signal on magnetron stability, noise and efficiency is therefore important. This paper discusses experiments with 2.45 GHz, 1 kW tubes and verifies our analytical model which is based on the charge drift approximation.

Kazakevich, G.↗

DOE OSTI2019

Subcritical-voltage magnetron RF power source

A system and method of operating a magnetron power source can achieve a broad range of output power control by operating a magnetron with its cathode voltage lower than that needed for free running oscillations (e.g., below the Kapitsa critical voltage or equivalently below the Hartree voltage) A sufficiently strong injection-locking signal enables the output power to be coherently generated and to be controlled over a broad power range by small changes in the cathode voltage. In one embodiment, the present system and method is used for a practical, single, frequency-locked 2-magnetron system design.

Kazakevich, Grigory M.↗

DOE OSTI2020

Subcritical-voltage magnetron RF power source

30 DIRECT ENERGY CONVERSION↗

DOE OSTI2017

Properties of Molybdenum Films Produced by High-Power Impulse Magnetron Sputtering

Results of experiments on deposition of thin molybdenum films on glass substrates by high-power impulse magnetron sputtering are presented. Two high-current modes with different pulse frequencies and durations are used. Properties of the produced molybdenum films are compared with those of films produced by magnetron sputtering at a direct current. It is shown that this method allows the resistivity of molybdenum films to be decreased and their reflectance in the visible range to be increased.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2018

Thermodynamic Investigation of the Effect of Target Compositions and Conditions of Their Magnetron Sputtering on Phase Compositions of the Resulting Films

A thermodynamic investigation of plasmochemical processes taking place in a magnetron during sputtering of the targets consisting of indium and dysprosium ions is performed, which allowed identifying the feasibility of forming under the given conditions certain amounts of the chemical compounds In{sub 2}O{sub 3}, Dy{sub 2}O{sub 3}, DyInO{sub 3}. In the thermodynamic analysis of the equilibrium compositions during magnetron sputtering of the films, a universal TERRA software program is used.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2018

Investigation of Corrosion Behavior of Ti/TiN Multilayers on Al7075 Deposited by High-Vacuum Magnetron Sputtering in 3.5% NaCl Solution

Although Al 7075 has many favorable mechanical properties such as the large strength-to-weight ratio, the relatively poor corrosion resistance has restricted industrial applications. In this work, Ti/TiN as hard multilayered and nanostructured coatings are deposited on the relatively soft Al 7075 structure by high-vacuum radio-frequency magnetron sputtering and the phase, structure, and morphology are investigated in details. The corrosion behavior is evaluated by electrochemical impedance spectroscopy in 3.5% NaCl at a pH of 7.5 for 1, 6, 12, 24, 36, 48, 60, and 72 h. At time points of 1, 6, 12, and 24 h, primary oxide layers and double layers are formed, but the corrosive medium penetrates the primary titanium nitride columnar structure. At longer time points of 24, 36, 48, 60, and 72 h, formation of stronger oxide and double layers leads to better corrosion resistance which is 14.8 times better than that observed from the uncoated substrate after immersion for 36 h. According to R{sub ct}, the corrosion resistances of the short and long immersion groups are 808.5-1984 and 808.5-1248 kΩ cm{sup 2}, respectively, thereby confirming the effectiveness of the Ti/TiN coating against corrosion in comparison with the corrosion resistance of 84.3 kΩ cm{sup 2} observed from the uncoated Al 7075. The smallest corrosion resistance of 808.5 kΩ cm{sup 2} observed at the time point of 24 h is 9.6 times that of the uncoated substrate. Graphical Abstract: A 1.4-µm-thick Ti/TiN hard nanostructured coating comprising six layers is deposited on the relatively soft Al 7075 substrate by high-vacuum radio-frequency magnetron sputtering at 100 °C. The first layer of the intermediate Ti layer cannot improve the corrosion resistance of the TiN super hard coating with a columnar structure. The second and third intermediate Ti layers play an important role in improving the corrosion resistance of Al 7075 by obstructing defects and coating damage from aggressive Cl{sup −} ions and penetration of water. The mechanism involves self-healing of defects by oxide formation and Warburg resistance by diffusion control. .

36 MATERIALS SCIENCE↗

DOE OSTI2021

Effects of sample bias on adhesion of magnetron sputtered Cr coatings on SiC

Swelling of SiC at 300 C due to in-service neutron irradiation causes tensile residual stresses in coatings which are expected to adversely affect the performance of coated SiC composite fuel cladding for light water reactors. Matching the coating swelling with the substrate, a solution common for thermal expansion, is not practical in the case of neutron irradiation. Biasing samples during magnetron sputtering deposition induces compressive residual stress which may counteract this. In this study, chromium coatings were deposited on SiC by DC magnetron sputtering with no external heating at bias voltages of –50V, –75V, and –100V. The effects of the bias voltage on morphology, residual stress, microstrain, texture, and adhesion are shown. The low deposition temperature resulted in the coating microstructure evolution following an energetic particle bombardment dominated trend. Additionally, at the two lower bias voltages knock-on implantation dominated increasing the residual stress and microstrain while at the highest bias voltage, thermal spike migration allowed for defect relaxation. When the knock-on induced compressive residual stress exceeded 0.8 GPa microcrack formation in the SiC substrate decreased coating adhesion. While no microcracks formed at the lowest bias voltage, insufficient atomic mobility during coating growth lead to voids forming in the coating. A balance is needed to form void-free coatings that have high compressive residual stress.

36 MATERIALS SCIENCE↗

DOE OSTI2017

Effect of Ar ion-beam-assistance and substrate temperature on physical properties of Al-doped ZnO thin films deposited by RF magnetron sputtering

Highlights: • AZO and IAZO (303–473 K) films were grown by RF magnetron sputtering technique. • Ar ion-beam converts its kinetic energy as diffusion energy to the deposited atoms. • Structural evolution relies on diffusion energy imparted to the deposited atoms. • Surface texture densify under the aid of ion-beam and substrate temperature. - Abstract: In this study, pronounced effects of ion-beam-assistance and substrate temperature were revealed by exploring the physical properties of Al-doped ZnO thin films deposited by the RF magnetron sputtering technique. Herein, two measurable parameters, ion-beam discharge current (0.1 A) and substrate temperature (303–473 K) were adopted to regulate the structural changes in Al-doped ZnO films. Specifically, progressive structural changes were achieved based on the addition of Ar ion-beam during the film growth. From XRD analysis, we observed significant structural changes that provided an improvement in the film growth towards c-axis (002) plane. In addition, FESEM and AFM analyses demonstrated excellent surface features with the assisted Ar ion-beam. As a result of this process, we effectively modulated the binding energy of Zn 2p level. Finally, the structural investigation accurately demonstrated that the dependence of assisted ion-beam and substrate temperature linearly related to the superior visible transmittance and reduced band gap.

36 MATERIALS SCIENCE↗